1. Field of the Invention
The present invention relates to a four-lens-group zoom lens system suitable for use in a photographic lens for a still camera, or a video camera and the like.
2. Description of the Related Art
A three-lens-group (substantially a four-lens-group) zoom lens system is proposed in Japanese Unexamined Patent Publication No. Hei-4-149402. However, such a zoom lens system, having the half angle-of-view of about 37.degree. at the short focal length extremity, cannot adequately meet the requirement of a wider angle-of-view than that of the above publication. Furthermore, since heavy lens elements on the side of an image are used for a focusing lens group, the load on the focusing lens mechanism is increased, which is disadvantageous for materializing automatic focusing. Japanese Unexamined Patent Publication No. Hei-6-75167 also teaches a four-lens-group zoom lens system, which is however insufficient from the viewpoint of a wider angle-of-view.